1. Technical Field of the Invention
The present invention relates to a method of manufacturing a device which is employed in electronic apparatuses, such as a liquid crystal display device (for example, a small-sized LCD or a large-sized LCD), a self light-emitting display device (for example, an organic EL display or a plasma display), and an LSI, and more specifically, to a method of manufacturing a device by forming thin films constituting the device using liquid materials, to a device obtainable through the method, and to an electronic apparatus comprising the device.
2. Description of the Related Art and Problems to be Solved by the Invention
In general, devices such as a thin film transistor comprise thin films, such as a semiconductor film, an insulating film or a conductive film. In a liquid crystal display device or the like, a transparent conductive film is also employed except the above films. Classifying these thin films in terms of their function, the insulating film includes a gate insulating film, and an interlayer insulating film, and the conductive film includes areas used as a gate electrode, source/drain electrodes, a pixel electrode and wiring.
As the semiconductor film, silicon films such as an amorphous silicon film or a poly-silicon film are mainly used. Conventionally, it is generally known that a device such as a thin film transistor using silicon was manufactured through the processes of forming a silicon film on the whole surface through a vacuum process such as a chemical vapor deposition (CVD) method, or a sputtering method and then removing unnecessary portions through photolithography. However, the CVD method has problems in that a large-scaled apparatus is required, the utilization efficiency of raw materials is low, the handling is difficult due to the use of gaseous raw materials, and a large quantity of waste is produced. Also, the sputtering method has problems common to the CVD method in that the film thickness at an uneven portion on a surface of a substrate is non-uniform, the productivity is low, and an apparatus is large-scale and expensive due to the required vacuum apparatus.
Recently, in place of such methods, a method of fabricating (or forming) a silicon film by applying a liquid high-order silane or a solution thereof to a substrate and by heating it or irradiating it with UV rays has been suggested. According to this method, the handling is easier due to the use of liquid raw materials and the silicon film can be formed at lower cost since a large-sized apparatus is not required. Further, by patterning the solution of high-order silane through the ejection of a droplet, the number of processes and the waste of material involved in the photolithography can be reduced.
A method of forming a silicon-group thin film by liquefying a gaseous raw material to cause it to be adsorbed onto a cooled substrate and then by causing it to react to atomic hydrogen in chemical activation is disclosed in Japanese Unexamined Patent Application Publication No. 1-29661. However, this method has the following problems. That is, since vaporizing and cooling silicon hydride as a raw material is carried out continuously, a complicated apparatus is not only required but also the control of film thickness is difficult.
Further, a method of forming a silicon film by applying liquid silicon hydride onto a substrate and heating it or irradiating it with UV rays is disclosed in Japanese Unexamined Patent Application Publication Nos. 5-1447141 and 7-267621. However, in this method, since materials having a low molecular weight are used, the system is unstable and thus the handling thereof is difficult. Furthermore, since the solution used in this method has a bad wettability to the substrate, the application thereof to the substrate is inherently difficult. In addition, since the materials have a low molecular weight, the boiling point thereof is low and thus the solution is vaporized prior to the formation of the silicon film during heating, so that it is very difficult to obtain a desired film. In other words, the way in which the high-order silane (of which the wettability is excellent, whose boiling point is high and which is secure) is used as the materials is a very important factor during the formation of a film.
As one solution thereof, a method for improving the wettability of a solution by thermally decomposing or photo-decomposing a mixture of high-order silane and a catalyst prior to the applying treatment is attempted in Japanese Unexamined Patent Application Publication No. 10-321536. However, in this method, there is a problem in that since mixing the catalyst such as nickel with the solution is required, features of the silicon film are remarkably deteriorated.
Generally, the composing order and the refining process are very difficult in a method of directly composing a silane compound having a large molecular weight. Although a method of directly composing the high-order silane by photopolymerization has also been attempted as disclosed in Japanese Unexamined Patent Application Publication No. 11-260729, the yield rate of Si9H20 is very low and such molecule size is still insufficient for the manifestation of performance such as wettability.
On the other hand, in a method of forming the silicon film containing n-type or p-type dopants, generally, the dopants are introduced using an ion implantation method after forming the silicon film. On the contrary, a method of forming a doped silicon film by mixing a dopant source with a material liquid during the formation of a silicon film made of the aforementioned high-order silane is disclosed in Japanese Unexamined Patent Application Publication No. 2000-31066. However, even in this method, since there are basic problems due to the use of the low molecule group material that the high-order silane solution is vaporized and reduced during heating and thus the dopant source is vaporized, it is difficult to effectively add the dopant.
Furthermore, even in forming the insulating film such as the gate insulating film or the interlayer insulating film or the conductive film for the electrode such as the gate electrode or the source/drain electrodes, which are used for a device such as a thin film transistor, the thermal CVD method, the plasma CVD method and the sputtering method are widely used similar to the aforementioned formation of the silicon film. The conductive film used for the device such as the thin film transistor is used as the gate electrode, the source/drain electrodes, wiring for connecting the electrodes to each other or power source wiring, and a metal film or a metal silicide film comprising Al, Cu, Cr, Ta or the like is used as a method of forming the conductive film. The conventional sputtering method is widely used for formation of the metal film or the silicide film. The device such as a thin film transistor used for a liquid crystal display device requires a transparent conductive film in addition to the conductive film. In general, the transparent conductive film includes an ITO film and is formed through the sputtering method similar to the formation of the metal film. However, the CVD method or the sputtering method still has the aforementioned problems.
Therefore, an object of the present invention is to provide a method of manufacturing a device at low cost using a small-sized and inexpensive apparatus, where the productivity is high, the defect rate is reduced, the production efficiency is high, disconnection does not occur in a stepped portion and the thin film is formed at low cost.